my $self = shift not only defines $self; it also modifies @_ (removing the first array item). The difference is only significant if you intend on using @_ or goto later on in the sub.

Update: Personally I've recently decided to adopt a coding style where I use shift for the invocant (i.e. $self or $class; but also "conceptual invocants" like $orig in Moose around method modifiers, or $ctx in Catalyst actions) and list assignment for other parameters.

For regular subs which are not intended to be called as methods, there is no invocant, so I just use list assignment to unpack all the arguments.

Why did I decide to adopt this style? I find it works nicely in terms of delegating method calls and so forth where you often need to pass on @_ to other methods and functions, but without passing on the invocant.

I'm not yet very strict with myself about this style, but hopefully it will become habit soon.